1. Field of the Invention
The present invention relates to a car navigation map update system for updating map data of a car navigation terminal.
2. Description of Related Art
Conventional car navigation electronic map systems usually store their map data in a read-only recording medium such as a CD-ROM, DVD-ROM or the like. Accordingly, to update their electronic map data, it is necessary to replace the recording medium itself that stores all the map data by a new version recording medium.
There is another type of map data update systems which do not replace their recording medium. For example, Japanese patent application laid-open No. 9-90869/1998 discloses a map associated information delivery system that employs, as a means for updating map data used by a car navigation device, a terminal (car navigation terminal) that calls up a host which keeps map update data, makes a request for desired map update data, and captures and utilizes the data as its own map update data.
With the foregoing configuration, the first type of the conventional car navigation map update systems present a problem when updating their electronic map data in that the recording medium itself must be replaced by a new version recording medium that stores all the map data.
The second type system that calls up the host has a problem of requiring a transmitter for sending the message to the host from the car navigation terminal, which complicates the system configuration and increases the cost.
The present invention is implemented to solve the foregoing problems. It is therefore an object of the present invention to provide a car navigation map update system and a car navigation terminal that can update map data by partially changing only updated map data without replacing all the map data, and that cat capture latest map data using only an already existing receiver installed in the car navigation system without using any additional transmitter.
According to a first aspect of the present invention, there is provided a car navigation map update system comprising: map update data delivery equipment including a map update data management section for managing a database containing rewritable map data, and a map update data broadcasting section for broadcasting by radio waves map update data rewritten by the map update data management section; and a car navigation terminal that receives the map update data broadcast by the map update data delivery equipment, stores the map update data in a map update data storing medium, and utilizes the map update data stored in the map update data storing medium in connection with map information data stored in a map data recording medium.
Here, the map update data management section and the car navigation terminal may form an entire map as an assemblage of partial map areas consisting of small subdivisions of map areas, and update the map on a partial map area basis by attaching an area identifier and a version number to each of the partial map areas.
The car navigation terminal may comprise a received data processor, wherein the received data processor may compare the area identifiers and version numbers of the received map update data with those of the map information data stored in the map data recording medium and with those of the map update data stored in the map update data storing medium; additionally store, when the received map update data includes a map update data block whose version number is newer than that of a corresponding map information data block stored in the map data recording medium, and whose area identifier disagrees with area identifiers of all map update data blocks on the map update data storing medium, the received map update data block into the map update data storing medium; and rewrite, when the received map update data includes a map update data block whose area identifier agrees with that of a map update data block stored in the map update data storing medium, and whose version number is newer than that of the map update data stored in the map update data storing medium, the map update data block on the map update data storing medium by the newly received map update data block.
The navigation terminal may comprise a map generator, wherein the map generator may retrieve map update data and map information data associated with designated map areas from the map update data storing medium and from the map data recording medium, and generate map data with replacing the map information data by the map update data in the designated map areas.
The map update data broadcasting section may broadcast the map update data repeatedly.
The car navigation map update system may further comprise a map update data update terminal, wherein the map update data storing medium may be removably attached to said car navigation terminal, and the map update data update terminal may rewrite the map update data on the map update data storing medium.
The map update data delivery equipment may comprise instead of the map update data broadcasting section an entire map data broadcasting section for broadcasting by radio waves all latest map data managed by the map data management section.
According to a second aspect of the present invention, there is provided a car navigation terminal comprising: a map data recorder for recording map data in advance; a receiver for receiving map update data broadcast by radio waves; a map update data storage for storing map update data; a received data processor that stores a map update data block in the received map update data when the map update data block is not stored in the map update data storage, and replaces, when a map update data block in the received map update data has its older version counterpart in the map update data storage, the older version counter part with the received map update data block; a map generator for combining map data recorded in the map data recorder with the map update data stored in the map update data storage; and a display unit for displaying combined map data.